Description

Light wave localisisation within the propagation channel is achieved through reflecting from the waveguide walls or due to focusing properties of the waveguide.

Of the many different classes of optical waveguides existing today the following three are the most promising and the most widely used: optical fibres, channel waveguides and planar waveguides.

The most important application for the optical fibres is the transfer of optical signals over long distances in communication systems. In addition, they are used for guided transmission of light energy in industrial laser systems and in laser medicine, as an active medium in fibre lasers and fibre amplifiers, in delay circuits, in non-linear optical signal processing systems, as sensing devices, and for many other purposes.

Communications systems usually use quartz optical fibres, whose characteristics are regulated by international standards. Long-range communication systems and urban communication networks use single-mode optical fibres, LAN networks and some access networks use multimode optical fibres. Polymer optical fibres and fibres with a quartz core and a polymer shell are used much less often and only for information transmission over short distances.

Special types of fibres, anisotropic fibres, large core diameter fibres, highly nonlinear fibres, etc., are used along with standard telecommunications fibres in many telecommunications applications.

Use of photonic crystal fibres and microstructured optical fibres provides for a better control of optical fields and signals, giving way to new practical applications.

Planar dielectric or semiconductor waveguides made of a thin film deposited onto a substrate and various types of channel optical waveguides are used to build photonic integrated circuits and planar optical devices.

A promising new type of channel optical waveguides is the planar waveguide based on photonic crystals (FC). In such waveguides a dielectric film restricts the light waves in the direction that is perpendicular to the film plane, and the two-dimensional FC structure localises and guides the light waves in the film plane.